LONDON, England (CNN) -- Authorities were investigating a suspicious package that was found Tuesday in the vicinity of the Bank of England, just two days before world leaders meet in London at the G-20 Summit.

CNN's Paula Newton said a controlled explosion was heard shortly after the package was discovered.

A spokesman for the Bank of England told CNN the building had not been evacuated.

The Bank of England was expected to be the focus of mass protests by anti-capitalist and climate change campaigners Wednesday on the eve of the G-20 meeting of world leaders in London.

Metropolitan Police leaders have warned that the city faces an "unprecedented" wave of protest in the run-up to Thursday's summit talks on the state of the global economy and are set to deploy huge numbers of officers to maintain public order.